Organic derivatives of cellulose



Patented Aug. 16, 1938 UNITED STATES ORGANIC DERIVATIVES OF CELLULOSEWilliam Whitehead, Cumberland, Md, assignor to Celanese Corporation ofAmerica, a corporation of Delaware No Drawing. Application September 30,1936, Serial No. 103,396

3 Claims.

This invention relates to the treatment of organic derivatives ofcellulose, such. as the organic esters of cellulose, to removetherefrom, or to make inactive, corrosive compounds or compounds thatcause the organic derivatives of cellulose to have a corrosive effect onmetallic surfaces. The so treated organic derivatives of cellulose maybe formed into filaments, films and molded articles without appreciablycorroding the spinning jets or other metallic surfaces contacted bysolutions of the organic derivative of cellulose.

An object of the invention is the economic and expeditious production oforganic derivatives of cellulose that, when dissolved in a solvent, formsolutions that are less corrosive than similar solutions formed ofuntreated organic derivatives of cellulose. Other objects of theinvention will appear from the following detailed description.

In the production of organic derivatives of cellulose there are producedvarious compounds that are either corrosive to metals or, when anorganic derivative of cellulose is dissolved in a solvent therefor,cause the formation of compounds that are .corrosive to metals. Examplesof one type of such compounds are those containing sulphur. Thesecompounds, prior to this invention, were separated from the derivativesof cellulose, if at all, only by elaborate and involved treatments. Byemploying this invention, however, organic esters of cellulose eitherbefore, during, or after being stabilized, are treated with an agentthat tends to remove corrosive compounds, or compounds which tend toproduce corrosive compounds. The treatment with the agent is simple andinexpensive. The treatment, in accordance with this invention is carriedout to such an extent as to produce an organic derivative of cellulosethat is substantially non-corrosive and is completed in a short periodof time. This treatment not only reduces to a negligible amount thecorrosiveness of the organic derivative of cellulose, but also removesor destroys those compounds which form insoluble filter blocking and jetblocking materials in spinning solutions. 1

Organic derivatives of cellulose treated in accordance with thisinvention may be spun into filaments by extruding the same through jetsinto a solidifying medium. The organic deriva-.

tive of cellulose so treated does not materially attack the metalsurrounding the orifice. When the metal of the spinning jet is attacked,the size of the orifice is enlarged or particles of the corroded metalwedged in the orifice, thus producing filaments of undesired denier.Furthermore, since organic derivatives of cellulose treated inaccordance with this invention do not attack metal parts contactedthereby, they do not pick up metallic salts which tend to discolorarticles formed therefrom.

In accordance with this invention, I treat precipitated or solid organicderivatives of cellulose, preferably at elevated temperatures, with adilute solution of an organic compound having a basic reaction, forexample, hydroxy amines, diamines, straight chain aliphatic amines andcyclic amines. After this treatment the derivatives of cellulose may beWashed substantially free of the treating compound and/or the reactionproducts formed by same or, if desired, at least a trace of the treatingcompound may be left in the derivative of cellulose. The organicderivative of cellulose may be treated before or after the treatmentwith the organic compounds having a basic reaction with chlorine or achlorine-liberating compound such as sodium hypochlorite. The organicderivative of cellulose thus treated, when dissolved in a solventtherefor, forms a solution which is substantially noncorrosive.

This invention is especially applicable to the treatment of anycorrosive organic esters of cel lulose such as cellulose acetate,cellulose formate, cellulose propionate and cellulose butyrate made byprocesses which tend to produce corrosive materials. It is alsoapplicable, in a general way, to the treatment of nitrocellulose,cellulose ethers and mixed esters and ethers of cellulose. Examples ofcellulose ethers are ethyl cellulose, methyl cellulose and benzylcellulose.

The organic esters of cellulose that lend themselves to this inventionmay be made by any of the methods now employed to make the same. Forexample, cellulose (cotton linters, cotton, Wood pulp, etc.) with orwithout a pretreatment in organic acid such as acetic acid and formicacid, is esterified by. treating the same with an acid anhydride in thepresence of an acid solvent and a catalyst. In place of the acid solventor in connection therewith there may be used suspension liquids such asbenzol. The acid solvent may be a concentrated acid corresponding to theanhydride employed or it may be, as is preferred, glacial acetic acid.Examples of catalysts are sulphuric acid, phosphorous acid, hydrochloricacid, Zinc chloride and mixtures of these.

After esterification, suflicient water may be added to convert anyremaining anhydride to the corresponding acid and the mixture hydrolizedor ripened until the desired solubility characteristics are developed.The catalyst is then neutralized and water or other non-solvent for theester added to precipitate the ester. During this precipitation step,the ester may, if desired, be treated with a solution of a hypochloriteor other chlorine-liberating compound to bleach the same. The ester isthen separated and washed free of the acid solution. The cellulose estermay then be stabilized by treating with boiling water containing smallamounts of mineral acid or with steam with or without pressure. Althoughstabilized, the ester may contain compounds which, when the ester is insolution, cause the solution to corrode or attack metals.

I have found that if the ester is treated after precipitation, but priorto stabilizing, by soaking able compounds may be removed or diminished.

to below an effective quantity by soaking the stabilized ester in adilute solution of an organic compound having a basic reaction. Thelatter method of treating stabilized esters is preferable as it is ingeneral more effective and has less tendency to alter viscosity andsolubility characteristics of the ester. The soaking treatment ispreferably carried on at elevated temperature, for instance, at from 50to 100 C. Although the soaking of the precipitated derivative ofcellulose in the dilute solution is the preferred method, other methodsmay be employed such as spraying the solution on the derivative ofcellulose, or working the derivative of cellulose in a countercurrentmanner in a stream of the dilute solution of the organic compound havinga basic reaction.

The treating liquid or bath may be formed by dissolving any suitableorganic compound having a basic reaction or suspending the same in anaqueous medium. As stated above, the organic compounds having a basicreaction may be hydroxy amines such as mono-, dior triethanolamine,di-amines such as ethylene diamines, straight chain aliphatic aminessuch as amylamines and cyclic amines such as pyridine, piccolines andlutidines. When treating organic esters of cellulose, the percentage ofthe organic compound in the treating bathshould be small enough so thatsubstantially no saponification or change in-viscosityof the esteroccurs. The amount of the aqueous solution or suspension of the organicbasic compounds is preferably from 4 to 20Tor. more times the weight ofthe derivative of cellulose, the;concentration being such that theamount of organic basic com pound used is between 0.03 to 1% on theweight of'the derivative of cellulose employed, andis preferably from0.1 to 0.5%. Although the treating bath may be of any suitabletemperature, for instance from 50 to 100 C., it has been foundpreferable to maintain the temperature at from C. to the boiling pointof the bath. Although an elevated'temperature is preferred, effectiveresults may be obtained at room temperature especially when employingcompounds most basic in reaction.

The treatment of the derivative of cellulose with the organic basiccompound may be precipitated or followed by a treatment with an alkalinehypochlorite. The alkaline hypochlorite treatment is not absolutelynecessary. The treatment with the organic basic compound is sufiicientto form non-corrosive derivatives of cellulose where it is undesirableto use thereon chlorine bleaching agents.

To further describe the invention and not as a limitation, the followingexamples are given:

Example I Stabilized cellulose acetate, washed neutral, is

'suitable solvent.

boiled with 364% by weight of the cellulose acetate of ethylene di-aminefor two hours and then again washed neutral, dried and dissolved in asuitable solvent. The cellulose acetate is found to be greatly improvedin its non-corrosive properties. For instance, the cellulose acetate isfound to be substantially non-corrosive to copper and but very slightlycorrosive to mercury and steel, whereas the original cellulose acetatewas corrosive to all three metals.

Example II Stabilized cellulose acetate, washed neutral, is boiled'with.8% tri-ethanolamine, by weight of the cellulose acetate, for twohours-and .then again washed neutral, dried and dissolved in a Thecellulose acetate is found to be greatly improved in its non-corrosiveproperties.

Example III Stabilizedv cellulose acetate, washed neutral, is boiledwith0.6%,by weight .of the cellulose acetate of amylamine for twohours andthen again washedneutral, dried and dissolved in a suitable solvent.The. cellulose acetateis found to be greatly improvedin itsnon-corrosive properties. During thetreatment a. strong odor ofhydrogensulphide is given off.

Example IV Stabilized cellulose acetate, washed neutral, is boiled with.04% .by. weight of the cellulose acetate of pyridine .for two hours andthen again washed. neutral, driedand dissolved in a suitablesolvent. Thecelluloseacetate is found to be greatly improved inits non-corrosiveproperties. During the treatment a strong odor of hydrogen sulphide isgiven off.

Itis. to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without :departingfrom the spirit of my invention.

Havingdescribed my invention, what I desire to.secure by Letters Patentis:

1. Method of reducingthe corrosive properties of. cellulose acetate,which comprises treatinga stabilized cellulose acetate with an aqueous.so-

lution containingfrom 0.3 to 1.0%, based onthe weight. of. the celluloseacetate present, of an organic base selected from the groupconsistingof'hydroxy amines, di-amines, straight chain ali-v phatic. amines, andcyclic amines.

2. Method of reducing the. corrosive properties of cellulose acetate,which comprises treating at a temperature of'from 50 to C. a stabilizedcellulose acetate with an aqueous solution con-- taining from 0.3 to1.0%, based on they weight of the. cellulose acetate present, .ofan'organic base. selectedfrom thev group consisting of hy droxy amines,di-amines, straight chain aliphatic taining, from 0.3-to 1.0%, based'onthe weight" of the cellulose acetate present, of an organicbase=selected-from the group'consisting-of hydroxy amines,-di-amines,s'traight'chain aliphatic amines and" cyclic amines.

WILLIAM WHITEHEAD.

